The embodiments disclosed herein relate to electrical components, and more particularly to the manufacture of electrical components from composite materials.
Transmission of low voltage digital, high frequency and other signals, including mixed mode signals over wired networks generally requires use of multi-element connectors which enable splicing of lengths and particularly long lengths of transmission lines together, or, to intersect or unite a signal source line together with several transmission reception lines. Optionally one or more of the intersecting connectors may provide a connection path for sensing and monitoring features of interest on or along the signal transmission line. Generally, all these connectors use metal contact elements to separably unite the signal path wires into an effective transmission network. The connector elements typically employ a mate-able contact pin and socket design for the primary signal conductor's path and one or more concentrically aligned, shield or ground path connector elements which may have a threaded barrel feature to the outermost metal connector element. Separation of the line while it is in service and used for active signal transmission can cause an undesired and potentially harmful spark or arc to occur. It would be a highly desired feature of the connector to enable reliable signal level connection while suppressing for example unwanted arcing upon separation of the active line or an element that is joined to the active line.
Further, automated testing of integrated circuit components as well as other active and passive circuit members including circuit boards is often conducted using a contact probe to temporarily connect the device under test (DUT) to a test instrument. A signal is communicated by the contact probe through a suitable interconnection, which may include electric cables, hook up wires, connectors, and the like to the instrument which can process and/or display details of interest relating to the signal(s) of interest. The instrument may be any applicable test instrument which may include a voltmeter, an ammeter, an ohm meter, a multimeter, an oscilloscope, and the like. The signal of interest stemming from the DUT may originate from operation of the device under actual use conditions, under simulation or stress conditions, or under a burn-in test protocol. Alternately, the instrument or related circuitry may provide a reference signal or power to the DUT while simultaneously extracting a sample return signal for characterization or display. Often, more than one probe is used to simultaneously monitor more than one signal and/or more than one location. The number of probes can be in the range of 10 to 100 or more. In this case, individual probes are arranged into an array of probes, which may be known by such terms as a bed-of-nails.
Characteristic of the probes in widespread contemporary use are probe elements having metal contact tips. The disadvantage of using metal-tipped probes is that under certain conditions the metal-to-metal contact between the probe and circuit member potentially can introduce an undesired electric bias or even a surge into the measurement, particularly in AC measurements owing to a capacitance and/or inductance the metal tip induces into the test circuit. In this case, inaccurate results are produced. Other disadvantages to the use of metal tip probes include; mechanical damage to the probe or to the circuit member such as scratching, denting, piercing, and even welding under high current conditions, contamination of the DUT due to transfer of metal surface oxides, and the like. A further disadvantage to metal probes used in large arrays is that they are generally heavy and require costly support structures to maintain positional precision.
Electric probes are also used in the medical industry and in the medical research field as temporary contacts to a wide range of materials and surfaces. These include such materials as human or animal skin, internal organs of the same, cells and groupings of cells, and the like. Often these probes are made from non-metal conductive materials such as inorganic salts in a suitable adhesive or gel medium which can adhesively join to and thereby serve to interconnect the surface of interest to a test instrument, such as an electrocardiogram monitor, a skin conductivity tester, and the like. The disadvantage to these non-metallic probes is that an adverse chemical reaction or allergic reaction may occur between the test subject and the contacting probe.
Certain electrical components used in electrostatographic printing machines are manufactured from composites, including composite plastics, that contain at least one filler which can be in the form of fine particles or fibers. The composites may be formed from a non-metallic pultruded composite member having multiple, generally circular cross section carbon fibers in a polymer matrix.
One of the difficulties with manufacturing such electrical components from composites has been in making thin disk-like elements or any configurations having thin sectional areas from, for example a pultruded carbon fiber filled rod such that the elements can be sized to fit into existing designs and packages, such as switch or integrated circuit packages, connector bodies, circuit board vias, and the like. Difficulties have been encountered with mechanically cutting small diameter composite rods into thin disks since the polymer matrix is frictionally heated and softened during the cutting process but then some of the polymer can condense or otherwise flow onto and around the ends of the fibers thereby contaminating the cut surfaces and preventing the necessary fiber-rich and/or pristine contact structure at the end of the disk. Laser cutting of such pultruded carbon fiber composite rods into thin disks has similarly proven difficult because the fibers conduct heat generated by the laser and the heat burns away the matrix polymer from around the fibers even at distances removed from the plane of the laser cut. Waterjet and laser milling of large diameter rods into somewhat smaller diameter rods has equally been problematic. The presence of microvoids and polymer-rich islands that can often exist within the cross section of the parent rod act to interrupt and/or diffuse the jet or beam in a manner that produces a flaw in the surfaces of the milled rod. These flaws are generally not acceptable to many applications that require a flaw-free surface on the rod or resultant discs produced from the rod. Similar difficulties are encountered in machining other composite materials and in forming shapes other than disks and rods. The difficulties are believed to stem from the differences in properties that exist between the filler or fillers used in the composite and the binder which is typically a polymer that serves to unify the composite into a solid structure, such as a rod. Particularly problematic is the case where the mass of filler(s) is a large fraction relative to the mass of the composite, for example equal to or more than about 10% by weight, and where the physical and/or geometric properties of the filler are greatly different from those of the host polymer. Typically the hardness of the filler is different, for example much greater than that of the polymer while often, at the same time, the size of the filler particles or fibers residing in the parent composition can be as large ore even much larger than the final thickness of a thin disc cut from the parent rod. Thus the jet of the fluid jet must pass trough both the filler phase(s) and the host polymer phase comprising the composite with equally effectiveness and without disturbing the compositional balance that exists or otherwise altering one phase with respect to the other or even to the parent composite.
It is known from commonly assigned U.S. Pat. No. 5,599,615 to make high performance electrical contacts that include a composite member with a plurality of electrically conductive, nonmetallic fibers in an electrically conductive metallic matrix. Further, U.S. Pat. No. 7,220,131 describes electromechanical devices having a plurality of bundles of fibers for interconnecting two planar surfaces which include surfaces of printed wiring boards and other related components. Composite plastics have not been used extensively in making signal transmission connectors, or test instrument or medical probe tips, however, because of such factors for example as limitations to critical electrical or mechanical property (CPs) tolerances and contact resistance predictability, as well as a lack of commercial availability.
It is known to use passive trimming in the electronics industry to remove material from a resistor to increase its electrical resistance. Known commercial processes employ a CO2, CO, Q-switched Yag, or other type of laser. However, lasers, along with all means of mechanical cutting (such as abrasive wheel, lathe milling, ElectroDischarge Machining (EDM) and Plunge EDM) are known to adversely affect the surface properties of certain types of components, and thus are unsuitable for certain applications. In U.S. Pat. No. 5,399,424, waterjet cutting is employed to cut thin disc-shaped members out of pultruded carbon fiber rods used in making electrical contacts.
It would be useful to develop fibrous electric components that have extremely precise electrical properties, including electrical resistance, and to provide manufacturing techniques and apparatus and apparatus for producing such components which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.